Independent screwed wellheads are well known in the art. The American Petroleum Institute (API) classifies a wellhead as an “independent screwed wellhead” if it possesses the features set out in API Specification 6A as described in U.S. Pat. No. 5,605,194 (Smith) entitled Independent Screwed Wellhead with High Pressure Capability and Method.
The independent screwed wellhead has independently secured heads for each tubular string supported in the well bore. Each head is said to be “independently” secured to a respective tubular string because it is not directly flanged or similarly affixed to the casing head. Independent screwed wellheads are widely used for production from low-pressure production zones because they are economical to construct and maintain.
While independent screwed wellheads have gained widespread acceptance in low-pressure applications, the ever-increasing demands for low-cost petroleum products mean that oil and gas companies must find innovative ways of further reducing exploration and extraction costs.
It is therefore highly desirable to provide a simple, cost-effective wellhead system and completion method which minimize drilling and completion expenses, thereby rendering the extraction of subterranean hydrocarbons more economical.